Considerable variation in response characteristics exists among blood vessels. However, little has been done to elucidate such variation in skeletal muscle vessels and the physiological function of such variations has yet to be established. The general aims of this study are to identify the endothelium and non-endothelium dependent responses which contribute to the regulation of vascular tone in skeletal muscle feed vessels and to determine if differences in these responses exist which may be related to the variation in oxidative capacity found among skeletal muscles. The first aim of this study is to evaluate the possibility that similarity in resting blood flow between muscles with very different maximal blood flow could be attributed to differences in myogenic tone or alpha adrenoreceptor mediated reactivity in their feed vessels. The second aim is to evaluate the possibility that differences in muscles' responses to vasodilator agents could be attributed to differences in adrenergic, muscarinic or purinergic influences on their feed vessels. Myogenic tension and tension development in response to agonists and blockers specific to these receptors will be measured in vitro using larger vessel techniques. Endothelium will be removed mechanically in half of the vessels and its presence will be verified in the other half. The dose-response characteristics of the soleus muscle's feed vessel and the extensor digitorum longus' feed vessel are compared using paired T analysis. The results of this investigation will enhance our understanding of both the functional significance of feed vessel heterogeneity and its role in the limitations of skeletal muscle performance.